A Hybrid Electric Vehicle (HEV) operates by buffering fuel energy by using the internal combustion engine to turn a generator; the electricity generated is stored in a battery. HEV systems can also recover kinetic energy by using the momentum of the vehicle to turn the generator; the electricity generated is then stored in a battery. Fuel is the predominate source of energy in an HEV system. Plug-in Electric Hybrid Vehicles (PHEVs) are an extension of existing hybrid electric vehicles (HEVs) with added energy flexibility. A PHEV utilizes a larger capacity battery pack than a standard HEV and the PHEV has two sources of energy, fuel and electricity from the electric utility grid.
An objective of the HEV control system is to minimize energy operational costs and emissions without compromising the vehicle drivability and system constraints. A standard Energy Management Control (EMC) strategy is traditionally designed to operate the HEV in electric drive mode in which the vehicle is operating only the electric motor to maximize the battery power output in blended operation mode, which is when the vehicle is operating both the engine and the electric motor.